1. Field of the Invention
A new type of gas heat engine is described that has several features similar to a gas turbine or jet engine. The engine is developed in many different configurations, each yielding different theoretical advantages and degrees of freedom. All of this family of engines have no moving components, provide heat recovery and operate over a wide range of input gas velocities. The new engines can use higher combustion temperatures and consequently have the potential for improved efficiency over current technology.
There are many theoretical and practical advantages to the new concepts, which give flexibility in both engine design and operating characteristics that are difficult to embody in current turbo jets. Among the most important is the potential for a thermodynamic efficiency which exceeds that of current open cycle gas heat engines at a given pressure ratio.
A new term in the equation of the Enthalpy of a gas is described, which could be exploited in yet other variants of the engine.
An application of special interest that emerges from this work is the potential to design first stage rocket boosters.
The substantiate benefits of the new engines are improved safety to aircraft, fuel economy, reduced engine weight, and cost. Furthermore, the engine concepts can be scaled to create engines of any desired size and power output without the conventional mechanical limits associated with gas turbines.
2. Background of the Related Art
A gas-turbine is an engine designed to produce useful energy (or work) output by deriving that energy from chemical energy produced by the combustion (or breakdown) of fuel. (e.g. Kerosene). (N.B.1). A gas turbine or jet engine, is the most powerful engine, (Megawatts/per unit volume and weight) known to man which is continuously rated. Rockets are more powerful but work intermittently, usually for only a few minutes.
A gas turbine consists essentially of three basic parts:                1. A compressor which derives working gas or fluid from the intake (e.g. air), and increases the pressure of the gas and supplies it to the combustion system. For compressible fluids (i.e. gases) an increase in temperature is also normally obtained.        2. A combustion system that supplies fuel which is burnt and in the process gives out energy in the form of heat.        3. A turbine which derives mechanical energy from the hot gas after the combustion process and recycles the energy, by a mechanical-link, to the compressor to do work on the input gas.        
Work left over at the output of the turbine is the useful work or energy output of the engine. Since the proportion of the energy derived from the gas by the turbine is reintroduced to the gas at the input to the engine by the compressor, these two components work ideally in a closed cycle, and are present to make the engine operate correctly by performing a thermodynamic cycle on the working fluid at the best possible efficiency. In practice both the compressor and turbine are a nuisance, because they are both less than 100% efficient thereby wasting useful work output, and they cause many other restrictions and difficulties which will be discussed later. (Sections 3, 4, 6 and Appendix 4). The useful work output appears as heat, velocity and increased pressure of the gas emerging from the engine. This energy can be used in a number of ways: In a jet engine it is used directly in the form of a force (thrust) to propel the engine forward when mounted in an aircraft. In ground installations it is used to drive another turbine whose mechanical energy is then employed to operate machinery or to generate electricity.
All gas turbines are governed by thermodynamic laws of physics, and are in the group generically known as heat engines. All operate in closed, partially closed or open forms of heat cycle. The theoretical maximum efficiency, or
  (            work      ⁢                          ⁢      output              heat      ⁢                          ⁢      input        )of heat engines has been well understood for decades. Carnot in 1824 was the first to calculate the basic rule for the theoretical efficiency of such engines. Nowadays there are more sophisticated ways of describing efficiency in terms of Entropy or Enthalpy diagrams and others. (N.B.2). However, for simplicity, the basic efficiency of an engine is related only to the ratio of the temperatures before and after the adiabatic compression of the input working fluid, where the temperatures are measured in degrees Absolute. (Kelvin).                Now if: η equals the efficiency in percent;        Tin equals the cold input gas temperature        Tcomp. equals the hot compressed gas temperature        
Then for an ideal engine the maximum possible efficiency is given by:
  η  =            (              1        -                              T            in                                T                          comp              .                                          )        ⁢    100  
It can be seen that if Tin is as low as possible, and Tcomp. is as high as possible, then the ratio of the two terms,
      (                  T        in                    T                  comp          .                      )    ,is small, and the efficiency is greatest.
For a typical jet engine the value of Tin might be 300° K (27° C.), and Tcomp. might be 600° K (327° C.), (Corresponding to a compression ratio of about 12 to 1).
      Then    ⁢                              ⁢                            ⁢    η    =            (              1        -                  300          600                    )        ×    100    ⁢                  ⁢    giving    ⁢                  ⁢    50    ⁢    %  
Unfortunately in practice losses of energy occur in all stages of actual gas turbines resulting in efficiencies usually in the range of 60 to 80% of the theoretical value. How these losses occur will be described later in Section 3. Suffice to say at this stage that the major losses are caused by the compressor and turbine. It can be seen that the higher the theoretical efficiency for a given percentage loss, then the higher will be the overall efficiency. It can also be seen that the limit is provided by the highest temperature point or combustion temperature of the cycle which must be higher than Tcomp., since it is impractical to reduce Tin. The combustion temperature in turn is limited by the hot strength of the turbine blades which are fully immersed in the gas exiting from the combustion process. In jet engines some 40 years of development has been devoted to the design of blades that will withstand higher and higher temperatures, and at the same time withstand large centrifugal forces. The use of single crystal alloys and all the skills of modern technology have given everyday engines which are only some 40% efficient. It is of interest to note what the progress has been:—The first flying Whittle engine in 1942 was about 10% efficient, and in 1982 the best (N.B.3) is about 40%, or on average an improvement of 30% in 40 years, or 0.75% per annum.
Since the compressor and turbine combination are needed to make the working fluid operate in a cycle, and do so by recirculating energy round the engine, and since the thermo/mechanical properties of the turbine blades limit the maximum temperature (or efficiency) of the cycle, it is essential in future developments to try to completely eliminate the turbine blade and hence the turbine from the operation of the engine. The limit on maximum temperature would then be mach higher and be caused instead by the heat resistance of the enclosing structure or body of the engine.
These structures can be lined with ceramics and locally cooled by bleeds of cool air, as is current practice for blades, combustion shields and other critical hot spots. It is not possible to make turbine blades of ceramics because they need a high strength to weight ratio due to the large centrifugal forces, whereas on body structures ceramics can provide the high temperature resistance and the metal backing the necessary strength.
It is therefore the elimination of the turbine can bring substantial benefits, but this would mean in turn that the compressor would also have to be eliminated, since there would be no source of mechanical energy to drive it. Some other new means of recirculating energy round the engine must be found to compress the input gas, and make it operate correctly and efficiently.